Alan's approach works fine, but considering your descriptions there, (Fault 1, Fault 2) maybe you want to create alarms for those values and just use the default (or a custom) alarm banner window.
You could also create 'Information Messages', which will pop up the default (or a custom) information banner window.
One other approach might be to create your pop-up windows, assign them a unique 'Display Number' on the Display Settings dialog, and configure a Global Connection (Remote Display Number) to the PLC to trigger those displays. Just set the PLC's remote display number back to zero to deactivate it after a second or so. Your pop-up will remain displayed (if it's set to 'On Top' until it is closed from the screen.